Producing aluminum-coated iron or steel



Patented July 6, 1948 UNITED STATES PATENT oerce PRODUCINGALUMINUM-COATED IRON STEEL Victor H. Bradford, Upper Montclair, N. J.,as-

signor to Specialties Development Corporation, Bloomfield, N. J., acorporation of New Jersey 1 No Drawing. Application September 7, 1942,

Serial No. 457,582

- iron and steel.

Another object is to provide an impervious aluminum coating for iron andsteel which precoating.

Another object is to provide iron and steel articles having an improvedaluminum coating.

Another object is to provide aluminum-coated iron or steel articles,which simulate aluminum articles and are as serviceable as aluminumarticles, but can be produced at a lower cost.

Another object is to provide an improved process of coating iron orsteel with aluminum.

A further object is to provide a simple and inexpensive process forcoating iron or steel with aluminum, and bonding or alloying the coatingto the iron or steel. I

Other and further objects of the invention will be obvious upon anunderstanding of theillustrative embodiment about to be described, orwill be indicated in the appended claim, and various advantages notreferred to herein will occur to one skilled in the art upon employmentof the invention in practice.

' In accordance with the invention, these objects aregenerallyaccomplished by subjecting an iron or steel base to anitrogenous medium, coating the "iron or steel base with aluminum, andcausing the coating to be bonded to the base. The nitrogenous mediumforms a superficial layer on the iron or steel which serves to bond oralloy the coating thereto.

Any suitable iron or steel may be used in con- 7 1 Claim. (Cl. JAB-46.6)

negligible aluminum content. The aluminum in such iron or steel ispresent as an impurity, rather than as an alloying ingredient.

Also, low alloying, high tensile steels, which a may be formed intostructural members and the like, are suitable for use in connection withpracticing the invention. Such steels usually contain between about .10and about .40 percent of carbon by weight. The aluminum content thereofis negligible, and is present as an impurityyrather than as an alloyingingredient.

The nitrogenous medium employed, preferably, is nascent nitrogen (N)produced by cracking ammonia gas at temperatures between about 1100 andabout 1150 F. 1

Any suitable types of commercially available aluminum may be used,ranging from substantially pure aluminum to various alloys of aluminum,wherein aluminum is the principal metal.

The aluminum coating maybe applied to sheets or plates, or the like, ofiron or steel adapted to be thereafter formed into articles, and maylikewise be applied to prefabricated iron orsteel articles. By the termbase, as used herein and in the appended claim, is meant the surface ofsheets, plates or the like, or the articles made therefrom.

In practice. the ferrous base to be coated is first cleaned anddegreased in any suitable or. customary manner. The base is thensubjected to nascent nitrogen at a temperature between about 950 andabout 1150 F., for a suillcient duration of time to produce anitrogenized or nitrogen treatedidentified as iron nitride. lheseneedles have a high afilnity faraluminum and readily alloy withaluminum, as will be described hereinafter.

The nitrogen treated or nitrogenized ferrous base is then coated withaluminum by electroplating, by dipping in a bath of molten aluminum, byspraying with aluminum, or in any other suitable manner. The thicknessof the coating may vary, depending upon the intended use of the coatedbase, or the character and intended use of the article or member madetherefrom. For example, the coating may have' a thickness of betweenabout-.0003 and about .010 inch.

After the coating of aluminum is applied, the base is passed through oris placed into a suitably heated furnace, oven or the like. Where theshape 0f the base permits, induction heating methods perature of betweenabout 400' and about 950 F.

higher heating temperatures, the heating period may be slightlyshortened.

The heating step causes the portion of the aluminum coating bontiguouswith the layer of nitrogenized iron to difiuse into the layer. Due tothe afiinity between aluminum and iron nitride, the portion of thealuminum coating in contact with the layer combines with the ironnitride to form a compound or complex comprising iron, aluminum andnitrogen. In this manner, the

aluminum is atomically bonded or alloyed with the ferrous base, to forma strong bond between the coating and the base. This enables the base tobe subjected to severe bending strains, deep drawing operations orpolishing operations without chipping, flaking, cracking, peeling orspalling of the aluminum coating.

From the foregoing description, it will be seen that the presentinvention provides improved aluminum-coated iron and steel, and aprocess of producing the same. The coating is integrally bonded oralloyed to the iron or'steel and will remain permanently thereon. Thecoating can readily withstand any rough usage to which it may besubjected.

The process employed is simple and inexpensive and does not involve theuse of complicated machinery, equipment or apparatus. Iron or steelplates, sheets or the like, coated in accordance with the process.herein, can be readily fabricated into articles heretofore made ofaluminum. Also, the articles formed of iron or steel may be thereaftercoated with aluminum by following the process of the invention. Theprocess likewise may be employed in connection with aluminum 4 coatingson previously used iron or steel articles or members, to recondition thesame.

As various changes may be made without departing from the spirit andscope of the inven- '7 tion, it is desired that the foregoingdescription be understood as illustrative and not in a limiting sense.

I claim:

The process iof aluminum coating an iron or steel base, which comprisessubjecting the base to nascent nitrogen at a temperature of betweenabout 950 and about 1150 F. for a time suflicient to produceasuperficial layer of iron nitride having a thickness of between about.0005 and about .001 inch, providing the base with an aluminum coatinghaving a thickness of between about .0003 and about .010 inch, andsubjecting the base and the coating to a temperature of between about400 and about 950 F. for a period of between 30 minutes and about 10hours to form an iron-nitrogen-aluminum complex between the base and thecoating adapted to alloy the coating to the base.

VICTOR H. BRADFORD.

REFERENCE S CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,409,017 Ortiz Mar. 7, 19221,552,041 Crapo Sept. 1, 1925 1,736,921 Kinzel Nov. 26, 1929 2,046,036Rodriguez I. June 30, 1936 2,135,388 Dellgren Nov. 1, 1938 2,197,622Sendzimir Apr. 16, 1940 OTHER REFERENCES Chemical Abstracts, September20, 1944, page 4900.

